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Interferon-gamma downregulates CFTR gene expression in epithelial cells
F Besançon1, G Przewlocki, I Baró
1Institut National de la Santé et de la Recherche Médicale Unité 245, Hôpital St.-Antoine, Paris, France.
The American Journal of Physiology
|November 1, 1994
Summary
Interferon-gamma (IFN-gamma) reduces cystic fibrosis transmembrane conductance regulator (CFTR) mRNA and protein levels. This cytokine impairs CFTR function, suggesting a role in inflammatory conditions affecting chloride transport.
Area of Science:
- Molecular Biology
- Cell Biology
- Immunology
Background:
- Cystic fibrosis (CF) is a genetic disorder caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, leading to impaired transepithelial chloride transport.
- The precise mechanisms regulating CFTR gene expression remain incompletely understood.
- Cytokines, such as interferons, are involved in immune responses and inflammation, but their specific impact on CFTR expression is not well-defined.
Purpose of the Study:
- To investigate the effect of different interferon subtypes on CFTR gene expression.
- To elucidate the regulatory mechanisms by which interferon-gamma (IFN-gamma) influences CFTR mRNA and protein levels.
- To assess the functional consequences of IFN-gamma-induced changes in CFTR expression on chloride transport.
Main Methods:
- Treatment of colon-derived epithelial cell lines (HT-29 and T84) with various interferon subtypes (IFN-gamma, IFN-alpha, IFN-beta).
- Quantification of CFTR mRNA levels and assessment of mRNA half-life.
- Measurement of CFTR protein levels and CFTR-mediated chloride transport (using 36Cl- efflux and whole-cell currents).
- Investigation of synergistic effects with tumor necrosis factor-alpha (TNF-alpha).
Main Results:
- IFN-gamma, but not IFN-alpha or IFN-beta, significantly downregulates CFTR mRNA levels in a time- and concentration-dependent manner.
- IFN-gamma reduces CFTR mRNA half-life, indicating posttranscriptional regulation through transcript destabilization, without affecting transcription rate.
- IFN-gamma treatment leads to decreased 165-kDa CFTR protein levels and diminished CFTR-mediated chloride transport function.
- IFN-gamma and TNF-alpha exhibit synergistic effects in reducing CFTR gene expression.
Conclusions:
- IFN-gamma exerts posttranscriptional regulation on CFTR expression, primarily by destabilizing CFTR mRNA.
- The observed reduction in CFTR protein and function suggests that IFN-gamma can impair chloride transport.
- Cytokine production during bacterial infections and inflammatory disorders may alter transmembrane chloride transport by modulating CFTR expression, potentially exacerbating CF-related pathology.